large organization nameservers sending icmp packets to dns servers.

Paul Vixie paul at
Thu Aug 9 00:35:39 UTC 2007

> >> ... but a TCP connection will consume a
> >> significant amount of a name server's resources.
> >
> > ...wrong.
> Wanting to understand this comment, ...

the resources given a nameserver to TCP connections are tightly controlled,
as described in RFC 1035 4.2.2.  so while TCP/53 can become unreliable during
high load, the problems will be felt by initiators not targets.

(this is why important AXFR targets have to be firewalled down to a very small
population of just one's own nameservers, and is why important zones have to
use unpublished primary master servers, and is why f-root's open AXFR of the
root zone is a diagnostic service not a production service.)

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